Billy Howle is terrific and Saoirse Ronan even better as a couple spending their fateful honeymoon in a hotel in 1962. To say they are inexperienced when it comes to sex is to understate the case considerably. This proves to be more than embarrassing fumbling, something much more deeply felt than that.

Geoffrey (Samuel West, left) and his son-in-law (Billy Howle) walk through his factory in "On Chesil Beach."(Photo: Robert Viglasky/Bleecker Street)

Florence Ponting (Ronan) is a serious student at Oxford, whose dream is to see the classical quartet she has founded become a going concern. (The withering looks she shoots bandmates are priceless.) Her father owns a factory; her mother is a classics professor.

Edward (Howle) has just graduated from the University of London (looked down upon by Florence’s family, of course). His father is an educator. His mother is a brain-damaged artist who flits about the house and yard in various states of undress and concentration, remembering little.

Florence and Edward first see each other by chance at a disarmament meeting. He thinks it’s love at first sight, and she’s agreeable with that position. They talk, they hang out, they have fun, they encourage each other’s dreams. She meets his family and brings his mother out of her shell, if temporarily; however briefly she connects, it’s a relief to the family. “Marry that girl,” his father instructs.

In "On Chesil Beach," Florence (Saoirse Ronan) dreams of a career with her classical quartet.(Photo: Robert Viglasky/Bleecker Street)

It’s a funny line (although he means it). And there is some humor here. Good thing. Hide the razors, otherwise.

We follow Edward and Florence on their wedding night — horrible British food served by nosy British waiters at a crummy British hotel with a spectacular British view right out the window. That will become important.

Everything leads to consummation, or at least an attempt at it. Florence, naturally, has researched the subject of sex and, along with her younger sister, found the prospect disgusting. Edward, meanwhile, can’t even lie about any former supposed conquests properly. Neither knows what to do, how to do, when to do. To put it simply — too simply — neither Florence nor Edward have a clue about the bedroom, despite Florence’s research and Edward’s empty boasts.

This is due, in large part, to the times. The sexual revolution is a few years away. Despite Florence’s political leanings, neither she nor Edward seem likely to lead the free-love charge.

We know this through the copious use of flashbacks. Overuse of flashbacks, sometimes, it seems. This is kind of a halfhearted complaint; it’s enjoyable just to watch Ronan and Howle in the various scenarios the film puts them in (McEwan wrote the screenplay).

When they finally get down to business a mishap, from Edward’s perspective, and a disaster from Florence’s (think: Edward’s a little too eager, though as clueless as Florence how to proceed) leads to her bolting the room.

Florence (Saoirse Ronan) is a bride in 1962 England in "On Chesil Beach."(Photo: Robert Viglasky/Bleecker Street)

What’s more, Florence simply has no use for it. Or, more accurately, she can’t stand it. As in, she wants more of a platonic relationship. Edward has no such idea in mind.

This all sounds like wedding-night jitters, probably, but it’s more than that. How that plays out you’ll have to discover for yourself. But there are a couple of scenes along the beach when Cooke expresses this visually with perfection. Think of the scene at the breakfast table from “Citizen Kane” played out among the rocks and waves.

A couple of latter scenes, not so much. (One in particular is not only unnecessary but heavy-handed and ridiculous.)

What never wavers is the quality of the acting. Both Ronan and Howle (who also appear together in the upcoming “The Seagull”) bring a great deal of truth to what by now are practically unthinkably naïve characters. Yet we recognize their frustration, their fear and, yes, their love. The question becomes how they will express it.